Let's call the wave of anti-Semitic threats and grave desecrations what they are: Terrorism.
No, nobody's been hurt. Doesn't matter. Terrorism uses violence to achieve political aims. In this case, the violence is threatened and implied, but the aim is clear: To intimidate American Jews and their allies.
This is not a problem that can be mitigated with promises that "I'm the least anti-Semitic person you've ever met." It requires leadership.